Introduction to Pharmacogenomics and Personalized Medicine. Pharmacogenomics is the field of selecting the right drug for the right patient at the right time. Its genesis was the belief that the pharmaceutical industry would identify and match patients with specific genetic phenotypes and gene expression profiles who would respond to specific therapeutic medicines, providing a new era of personalized medicine. This would inherently enhance the drugs therapeutic profile, resulting in more successful clinical trial results as the selected patients would have already been identified as potential responders to the therapy. An example of a successful drug that has been developed using the concept of pharmacogenomics is the drug Herceptin. It is currently used in the treatment of early stage Human Epidermal growth factor Receptor-2 (HER-2) positive and late stage HER-2 positive metastatic breast cancer where an overexpression of the protein marker HER-2 is caused by a gene mutation in the cancerous cell. This genetic mutation is present in one out of every five breast cancers. Herceptin specifically targets HER-2 to kill the cancer cells and is often used with chemotherapy to decrease the risk of cancer recurrence. Therefore, patient testing HER-2 positive is a pre-specified requirement for treatment with Herceptin.
The concept of selecting patients who are predisposed to respond to particular therapies has tremendous potential. A number of efforts have been put forth in the development of gene expression assays to characterize cancer tumors based on their gene activity—i.e., up regulation or down regulation of specific genetic markers or a genetic mutation specific to the type of cancerous cells. These gene expression assays would allow a more accurate understanding of the cause of the disease from a genetic standpoint which would result in the ability to pinpoint the specific pathway via which these genes are getting up or down regulated or mutated. Therefore, a patient's responsiveness to expensive and often dangerous chemotherapy that is not specifically tailored to the patient's individual needs, could be evaluated in advance of the therapy which would reduce cost but above all, would prevent the patient from going through unnecessary painful treatments. Genomic Health's OncotypeDx gene expression assay is an example of such a product which is generating millions of dollars per year as a diagnostic assay to determine whether or not a patient has a high likelihood of responding to therapy. Other new products on the market, CareDx's Allomap assay and CardioDx's Corus test are designed to determine whether or not a patient should be subjected to a more invasive assay to assess the status of the disease. For CareDx's Allomap assay, gene expression analysis of the circulating white cells in the blood is intended to determine if the patient's circulating immune system is calm or angry. If calm, the patient does not need to have an invasive heart biopsy and may even have their dosage of potentially dangerous immunosuppressant drugs lowered. If angry, the patient needs to have a biopsy, which, if positive, is likely to result in an increased immunosuppression regimen. For the CardioDx Corus test, the blood based leukocyte gene expression signature is used to safely and quickly help identify whether a patient presenting with chest pain is likely suffering from obstructive coronary artery disease and would require a coronary angiogram to look for a diseased artery or a heart attack. These are merely three examples of a new field of endeavor in which patient specific information is used to help determine appropriate next steps for informed patient care management. This may and oftentimes does include significant and expensive clinical care decisions, and these tests therefore have value in both mitigating the risks of unnecessary and potentially dangerous procedures and reducing medical costs.
Introduction to Autologous Tissue Therapies.
In medicine, there are many autologous therapies in which a tissue or material is extracted from a patient and is returned to the patient for therapeutic purposes. Autologous therapies can be classified as homologous and non-homologous. Homologous autologous therapies constitute harvesting a tissue from one part of the body and using it to serve the same basic function whether it is in the same or a different part of the body of a patient. Examples of homologous autologous therapies include the harvest of skin from a less visible part of the body to perform a graft on the face of a burn victim; the use of bone from one part of the body to help reconstruct another more important and critical bone structure; and the extraction of cartilage from one part of the body and its ex vivo culture and expansion for re-implantation into the body later. Non-homologous therapies are those in which the harvested tissue and preparations thereof either by concentration, selection, expansion, modification by adding ligands, culture or any combinations of these are intended to serve a different purpose than the tissues were serving at their time of harvest. This does not mean they may not mimic natural processes, but rather that they were harvested and are being repurposed from their status at time of harvest. Non-homologous cell therapies include the delivery of cells or tissues to treat cardiovascular disease, autoimmune diseases, diabetes, metabolic disorders, and a broad variety of cancers.
Cardiovascular indications include acute myocardial infarction, chronic myocardial ischemia, heart failure of ischemic etiology (with active ischemia or chronically infarcted without the presence of active ischemia) or non-ischemic etiology, or cardiac arrhythmias, refractory angina, dilated cardiomyopathy. U.S. Pat. No. 7,097,832 issued to Kornowski and U.S. Pat. No. 8,496,926 issued to de la Fuente describe such therapeutic strategies to treat cardiovascular disease using bone marrow derived cells. Autologous non-homologous tissues that have been investigated preclinically and clinically for such non-homologous cardiac therapeutic purposes are extensive and include bone marrow cells, bone marrow or peripheral blood mononuclear cells, bone marrow or blood derived CD34 cells (whether harvested from the bone marrow or from the blood after GCSF stimulated release), bone marrow or blood derived CD133 cells; bone marrow or blood derived CD 19 cells, bone marrow or blood derived ALDH bright positive cells, bone marrow derived and ex vivo expanded mesenchymal cells, bone marrow derived and expanded mesenchymal precursor or progenitor cells, adipose tissue derived cells, and umbilical cord derived cells. Other non-homologous tissues that have been used preclinically include c-kit+ cells, placental-derived cells, human amniotic mesenchymal stem cells. Many of these autologous therapies have been indicated for the treatment of other diseases such as chronic limb ischemia and intermittent claudication as well as autoimmune and inflammatory diseases such as inflammatory bowel diseases of ulcerative colitis, Crohn's disease, lupus, osteoarthritis, diabetes and kidney diseases.
The use of activated T-cells, tumor infiltrating leukocytes, and activated dendridic cells have an expanding role in immunotherapy today and often involve removing dendritic cells or t cells from the patient and modifying them to enable them to more accurately and aggressively attack tumor cells when they are re-administered to the patient. Dendritic cells are antigen-presenting cells, (also known as accessory cells) of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. Dendritic cells act as messengers between the innate and the adaptive immune systems. T cells or T lymphocytes are a type of lymphocyte (a type of white blood cell) that play a central role in cell-mediated immunity, They can be distinguished from other lymphocytes, such as B cells and natural killer cells (NK cells), by the presence of a T-cell receptor (TCR) on the cell surface. They are called T cells because they mature in the thymus (although some also mature in the tonsils). There are several subsets of T cells, each with a distinct function.
Tissue based autologous therapies, by their nature are personalized and depend on a number of variables including the patient's age, sex, race, weight, extent of cardiovascular disease progression and the presence of comorbidities such as diabetes, hypertension, angina, hyperlipidemia among others. All patients do not have the same cells in the same concentrations with the same genes or gene expression profiles. All patients do not have the same therapeutic potential in their tissues for a given clinical indication nor will all patients respond to a therapy identically even if the therapeutic potential of a given dosage form is identical. This is a critical problem in the field.
Different approaches have been used to try and solve various aspects of this problem, with particular focus on cardiovascular disease, the leading cause of death in the western world. One potential solution is to attempt to make autologous cell therapy as close to a pure pharmaceutical preparation as possible. Examples of such autologous cell therapy products for just cardiovascular applications include Baxter's or Neostem's selected CD34 cells in chronic myocardial ischemia and acute myocardial infarction, respectively; CellProThera's culture expanded CD34+ cells; Miltenyi's selected CD133 cells), culture-expanded Mesenchymal Stem Cells (MSCs), Dental Pulp Stem Cells (DPSCs), Cardio3 Biosciences culture expanded MSCs with ex vivo stimulated differentiation, Capricor's culture expended cardiosphere derived cells, autologous culture expanded CD271 positive cells, and expanded Hematopoietic Stem Cells (HSCs), and the like. Such autologous cell therapy products require extensive manipulation and analysis of the cells intended for treatment before they are returned to the patient to enable dosage formulations which are as standardized as possible. The cell manipulation often requires isolating cells with specific cell surface markers such as CD34 or CD133 from bone marrow or peripheral blood using antibodies bound to magnetic beads or other standard purification methods and expanding those isolated cell populations in culture outside of the patient's body to reach the desired dosage formulation required for treatment. That dosage could be determined based on patient weight or could be a same standardized dosage in terms of total number of cells to be delivered. Cell analysis usually includes performing functional assays such as mitogenic or colony forming unit assays (CFU-F, CFU-EC, CFU-HILL, etc.) on these cells to determine the cells' health and their proliferative potential. These types of extensive manipulation, cell culture handling and analysis significantly raise the costs of these proposed therapeutic candidates. Not only do the manipulations themselves have significant labor and complex reagents and materials costs, but they also have shipping and quality control costs on each patient's tissues, resulting in a separate manufacturing lot for each and every dosage form for one particular patient. Each assay on a potential autologous therapeutic dosage formulation and each step in its handling add significantly to the costs of the therapy—which in turn means that the developer and manufacturer will ultimately have to charge a higher price for their product. This approach however only addresses one issue by attempting to normalize the dosage in every patient but still does not result in identical dosages for these patients as we can only suggest that the cells performed similarly in the functional assays involved and passed the lot release testing specified by the developer for purity, functional assay, sterility and lack of contamination by infectious agents. This does not mean that the cells would behave the same way when re-injected in the patient. One example of an autologous cell therapy product for cardiovascular application that employed this selected cell strategy with a successful clinical trial outcome lies in Baxter's CD34 autologous cell therapy. The double-blind, prospective, randomized, placebo-controlled Phase II trial was designed to determine the tolerability, efficacy, safety, and dose range of intramyocardial injections of G-CSF mobilized autologous CD34 cells for a reduction of angina episodes in patients with refractory chronic myocardial ischemia (ACT34-CMI). The results of this trial published in Losordo D W et al. 2011 [Circ Res. 109: Intramyocardial, Autologous CD34+ Cell Therapy for Refractory Angina] have shown that percutaneous intramyocardial injections of mobilized autologous peripheral blood derived CD34+ cells at dosages of 105 cells/kg led to significant improvements in angina frequency and exercise tolerance.
Other purified cells with specific cell surface markers isolated from the bone marrow, include the CD19 bone marrow derived cells which have been shown to have potential efficacy that is superior to that of whole bone marrow or other cell subtypes in preclinical studies (Goodchild T et al. 2009, J Am Coll Cardiol Intv. 2: 1005-16). These cells are described in U.S. Pat. No. 7,695,712.
A second approach to the problem is to increase the uniformity of therapeutic cells delivered to each patient and eliminate the costs of analyzing the cells and of manufacturing a separate lot for each dosage formulation through the development of allogeneic tissue dosage formulations so that the tissue from one donor can be applied to thousands of patients. This strategy was previously in development by Osiris Therapeutics with Mesenchymal Stem Cells, and is currently being developed by Mesoblast with Mesenchymal Precursor Cells. Mesenchymal stem cells (or precursor cells or progenitor cells) have long been argued to be immune privileged cells such that the allogeneic donor cells will not be attacked by the circulating immune system of the recipient, thus making the possibility of a universal donor a realistic and extremely attractive one. In addition to being obviously more cost effective and commercially viable, this strategy, also has the advantage of enabling the selection of healthy young donors whose healthy cells have been shown to be much more efficacious that the older diseased patients' cells. Other groups including Capricor Therapeutics, Inc., a clinical stage biotechnology company that has migrated to developing allogeneic cardiac stem cells (CSC) after reporting results from autologous cells, has postulated that their allogenic CSC are not immune privileged as the allogeneic mesenchymal stem cells. The Capricor allogenic CSC are rejected or eliminated from the heart, but the cells are reported to have their therapeutic benefit before being rejected by the immune system of the recipient or otherwise eliminated. The problem with this therapeutic approach even if the theoretical assertions on the immune privilege status of mesenchymal stem cells or time course of action preceding rejection for CSCs hold true, is that each lot of cells will come from a different universal donor or a combination of donors and they will not be identical. Therefore, to a lesser extent, as in the first approach above, one should expect variations in response and in beneficial outcomes with each donor or batch lot and at present, one cannot presume these variations to be insignificant or predictable.
These current approaches for specific strategies for cell therapies are based on the classical pharmaceutical mindset of purification to optimize a dosage form that is the same for all patients, even if it is an autologous therapy. While this has value for advancing the status of our scientific knowledge and adds significant rigor to cell based therapies, it also adds enormously to the complexity of therapies when simpler approaches described herein are possible. Both of these approaches are intended to overcome what is seen as limitations with respect to the delivery of minimally processed bone marrow (in development by T2Cure, Harvest, Biomet, Thermogenesis, and others) or adipose stromal cells or adipose derived regenerative cells (Cytori Therapeutics and others) which are viewed as more variable from patient to patient.
US Patent Publ. 2010/0127342 describes how gene expression profiles from autologous cells could be developed to select patients for a given therapeutic strategy based on their likelihood of being responders to such a therapy. This is hereby included by reference, along with the references cited therein. Personalized medicine strategies for autologous tissue based therapeutics have significant potential that is not well appreciated as the diagnostic assessment of a patient's potential responsiveness can also be an analysis of the autologous dosage form's therapeutic potency.
Signature to Gate Dosage of Autologous Bone Marrow Cells for Cardiac Repair in a Setting of Heart Failure of Ischemic Etiology, with or without Evidence of Active Ischemia.
Delivery of autologous mononuclear cells derived from the bone marrow has been shown to be consistently safe in the setting of chronic heart failure, chronic myocardial ischemia, and acute myocardial infarction. However, while there is consensus about the safety of these cells, efficacy results from similar clinical studies in the same patient population appear to be inconsistent. Dosage is believed to be a primary culprit driving these inconsistencies. Consistent with this hypothesis, is the observation that trials with lower dosages of these cells, whether by design or due to delivery via the coronary artery route of administration have fewer positive trial results, and studies with higher cell dosages have greater rates of success. However, it is noted that higher dosage does not necessarily correlate to greater efficacy. This was observed in the Baxter study (Losordo et al. 2011) using mobilized autologous peripheral blood derived CD34+ cells in a patient population with chronic myocardial ischemia for the treatment of refractory angina whereby the smallest CD34+ cell dosage of 105 cells/kg had the most significant positive efficacy results. Variations between patients in cell potency and in cell dosage delivered may also result in failed therapeutic efficacy trials.